1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * The Internet Protocol (IP) module. 7 * 8 * Authors: Ross Biro 9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 10 * Donald Becker, <becker@super.org> 11 * Alan Cox, <alan@lxorguk.ukuu.org.uk> 12 * Richard Underwood 13 * Stefan Becker, <stefanb@yello.ping.de> 14 * Jorge Cwik, <jorge@laser.satlink.net> 15 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 16 * 17 * 18 * Fixes: 19 * Alan Cox : Commented a couple of minor bits of surplus code 20 * Alan Cox : Undefining IP_FORWARD doesn't include the code 21 * (just stops a compiler warning). 22 * Alan Cox : Frames with >=MAX_ROUTE record routes, strict routes or loose routes 23 * are junked rather than corrupting things. 24 * Alan Cox : Frames to bad broadcast subnets are dumped 25 * We used to process them non broadcast and 26 * boy could that cause havoc. 27 * Alan Cox : ip_forward sets the free flag on the 28 * new frame it queues. Still crap because 29 * it copies the frame but at least it 30 * doesn't eat memory too. 31 * Alan Cox : Generic queue code and memory fixes. 32 * Fred Van Kempen : IP fragment support (borrowed from NET2E) 33 * Gerhard Koerting: Forward fragmented frames correctly. 34 * Gerhard Koerting: Fixes to my fix of the above 8-). 35 * Gerhard Koerting: IP interface addressing fix. 36 * Linus Torvalds : More robustness checks 37 * Alan Cox : Even more checks: Still not as robust as it ought to be 38 * Alan Cox : Save IP header pointer for later 39 * Alan Cox : ip option setting 40 * Alan Cox : Use ip_tos/ip_ttl settings 41 * Alan Cox : Fragmentation bogosity removed 42 * (Thanks to Mark.Bush@prg.ox.ac.uk) 43 * Dmitry Gorodchanin : Send of a raw packet crash fix. 44 * Alan Cox : Silly ip bug when an overlength 45 * fragment turns up. Now frees the 46 * queue. 47 * Linus Torvalds/ : Memory leakage on fragmentation 48 * Alan Cox : handling. 49 * Gerhard Koerting: Forwarding uses IP priority hints 50 * Teemu Rantanen : Fragment problems. 51 * Alan Cox : General cleanup, comments and reformat 52 * Alan Cox : SNMP statistics 53 * Alan Cox : BSD address rule semantics. Also see 54 * UDP as there is a nasty checksum issue 55 * if you do things the wrong way. 56 * Alan Cox : Always defrag, moved IP_FORWARD to the config.in file 57 * Alan Cox : IP options adjust sk->priority. 58 * Pedro Roque : Fix mtu/length error in ip_forward. 59 * Alan Cox : Avoid ip_chk_addr when possible. 60 * Richard Underwood : IP multicasting. 61 * Alan Cox : Cleaned up multicast handlers. 62 * Alan Cox : RAW sockets demultiplex in the BSD style. 63 * Gunther Mayer : Fix the SNMP reporting typo 64 * Alan Cox : Always in group 224.0.0.1 65 * Pauline Middelink : Fast ip_checksum update when forwarding 66 * Masquerading support. 67 * Alan Cox : Multicast loopback error for 224.0.0.1 68 * Alan Cox : IP_MULTICAST_LOOP option. 69 * Alan Cox : Use notifiers. 70 * Bjorn Ekwall : Removed ip_csum (from slhc.c too) 71 * Bjorn Ekwall : Moved ip_fast_csum to ip.h (inline!) 72 * Stefan Becker : Send out ICMP HOST REDIRECT 73 * Arnt Gulbrandsen : ip_build_xmit 74 * Alan Cox : Per socket routing cache 75 * Alan Cox : Fixed routing cache, added header cache. 76 * Alan Cox : Loopback didn't work right in original ip_build_xmit - fixed it. 77 * Alan Cox : Only send ICMP_REDIRECT if src/dest are the same net. 78 * Alan Cox : Incoming IP option handling. 79 * Alan Cox : Set saddr on raw output frames as per BSD. 80 * Alan Cox : Stopped broadcast source route explosions. 81 * Alan Cox : Can disable source routing 82 * Takeshi Sone : Masquerading didn't work. 83 * Dave Bonn,Alan Cox : Faster IP forwarding whenever possible. 84 * Alan Cox : Memory leaks, tramples, misc debugging. 85 * Alan Cox : Fixed multicast (by popular demand 8)) 86 * Alan Cox : Fixed forwarding (by even more popular demand 8)) 87 * Alan Cox : Fixed SNMP statistics [I think] 88 * Gerhard Koerting : IP fragmentation forwarding fix 89 * Alan Cox : Device lock against page fault. 90 * Alan Cox : IP_HDRINCL facility. 91 * Werner Almesberger : Zero fragment bug 92 * Alan Cox : RAW IP frame length bug 93 * Alan Cox : Outgoing firewall on build_xmit 94 * A.N.Kuznetsov : IP_OPTIONS support throughout the kernel 95 * Alan Cox : Multicast routing hooks 96 * Jos Vos : Do accounting *before* call_in_firewall 97 * Willy Konynenberg : Transparent proxying support 98 * 99 * 100 * 101 * To Fix: 102 * IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient 103 * and could be made very efficient with the addition of some virtual memory hacks to permit 104 * the allocation of a buffer that can then be 'grown' by twiddling page tables. 105 * Output fragmentation wants updating along with the buffer management to use a single 106 * interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet 107 * output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause 108 * fragmentation anyway. 109 * 110 * This program is free software; you can redistribute it and/or 111 * modify it under the terms of the GNU General Public License 112 * as published by the Free Software Foundation; either version 113 * 2 of the License, or (at your option) any later version. 114 */ 115 116 #define pr_fmt(fmt) "IPv4: " fmt 117 118 #include <linux/module.h> 119 #include <linux/types.h> 120 #include <linux/kernel.h> 121 #include <linux/string.h> 122 #include <linux/errno.h> 123 #include <linux/slab.h> 124 125 #include <linux/net.h> 126 #include <linux/socket.h> 127 #include <linux/sockios.h> 128 #include <linux/in.h> 129 #include <linux/inet.h> 130 #include <linux/inetdevice.h> 131 #include <linux/netdevice.h> 132 #include <linux/etherdevice.h> 133 134 #include <net/snmp.h> 135 #include <net/ip.h> 136 #include <net/protocol.h> 137 #include <net/route.h> 138 #include <linux/skbuff.h> 139 #include <net/sock.h> 140 #include <net/arp.h> 141 #include <net/icmp.h> 142 #include <net/raw.h> 143 #include <net/checksum.h> 144 #include <linux/netfilter_ipv4.h> 145 #include <net/xfrm.h> 146 #include <linux/mroute.h> 147 #include <linux/netlink.h> 148 149 /* 150 * Process Router Attention IP option (RFC 2113) 151 */ 152 bool ip_call_ra_chain(struct sk_buff *skb) 153 { 154 struct ip_ra_chain *ra; 155 u8 protocol = ip_hdr(skb)->protocol; 156 struct sock *last = NULL; 157 struct net_device *dev = skb->dev; 158 159 for (ra = rcu_dereference(ip_ra_chain); ra; ra = rcu_dereference(ra->next)) { 160 struct sock *sk = ra->sk; 161 162 /* If socket is bound to an interface, only report 163 * the packet if it came from that interface. 164 */ 165 if (sk && inet_sk(sk)->inet_num == protocol && 166 (!sk->sk_bound_dev_if || 167 sk->sk_bound_dev_if == dev->ifindex) && 168 net_eq(sock_net(sk), dev_net(dev))) { 169 if (ip_is_fragment(ip_hdr(skb))) { 170 if (ip_defrag(skb, IP_DEFRAG_CALL_RA_CHAIN)) 171 return true; 172 } 173 if (last) { 174 struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC); 175 if (skb2) 176 raw_rcv(last, skb2); 177 } 178 last = sk; 179 } 180 } 181 182 if (last) { 183 raw_rcv(last, skb); 184 return true; 185 } 186 return false; 187 } 188 189 static int ip_local_deliver_finish(struct sk_buff *skb) 190 { 191 struct net *net = dev_net(skb->dev); 192 193 __skb_pull(skb, ip_hdrlen(skb)); 194 195 /* Point into the IP datagram, just past the header. */ 196 skb_reset_transport_header(skb); 197 198 rcu_read_lock(); 199 { 200 int protocol = ip_hdr(skb)->protocol; 201 const struct net_protocol *ipprot; 202 int raw; 203 204 resubmit: 205 raw = raw_local_deliver(skb, protocol); 206 207 ipprot = rcu_dereference(inet_protos[protocol]); 208 if (ipprot != NULL) { 209 int ret; 210 211 if (!ipprot->no_policy) { 212 if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 213 kfree_skb(skb); 214 goto out; 215 } 216 nf_reset(skb); 217 } 218 ret = ipprot->handler(skb); 219 if (ret < 0) { 220 protocol = -ret; 221 goto resubmit; 222 } 223 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 224 } else { 225 if (!raw) { 226 if (xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 227 IP_INC_STATS_BH(net, IPSTATS_MIB_INUNKNOWNPROTOS); 228 icmp_send(skb, ICMP_DEST_UNREACH, 229 ICMP_PROT_UNREACH, 0); 230 } 231 kfree_skb(skb); 232 } else { 233 IP_INC_STATS_BH(net, IPSTATS_MIB_INDELIVERS); 234 consume_skb(skb); 235 } 236 } 237 } 238 out: 239 rcu_read_unlock(); 240 241 return 0; 242 } 243 244 /* 245 * Deliver IP Packets to the higher protocol layers. 246 */ 247 int ip_local_deliver(struct sk_buff *skb) 248 { 249 /* 250 * Reassemble IP fragments. 251 */ 252 253 if (ip_is_fragment(ip_hdr(skb))) { 254 if (ip_defrag(skb, IP_DEFRAG_LOCAL_DELIVER)) 255 return 0; 256 } 257 258 return NF_HOOK(NFPROTO_IPV4, NF_INET_LOCAL_IN, skb, skb->dev, NULL, 259 ip_local_deliver_finish); 260 } 261 262 static inline bool ip_rcv_options(struct sk_buff *skb) 263 { 264 struct ip_options *opt; 265 const struct iphdr *iph; 266 struct net_device *dev = skb->dev; 267 268 /* It looks as overkill, because not all 269 IP options require packet mangling. 270 But it is the easiest for now, especially taking 271 into account that combination of IP options 272 and running sniffer is extremely rare condition. 273 --ANK (980813) 274 */ 275 if (skb_cow(skb, skb_headroom(skb))) { 276 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 277 goto drop; 278 } 279 280 iph = ip_hdr(skb); 281 opt = &(IPCB(skb)->opt); 282 opt->optlen = iph->ihl*4 - sizeof(struct iphdr); 283 284 if (ip_options_compile(dev_net(dev), opt, skb)) { 285 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 286 goto drop; 287 } 288 289 if (unlikely(opt->srr)) { 290 struct in_device *in_dev = __in_dev_get_rcu(dev); 291 292 if (in_dev) { 293 if (!IN_DEV_SOURCE_ROUTE(in_dev)) { 294 if (IN_DEV_LOG_MARTIANS(in_dev)) 295 net_info_ratelimited("source route option %pI4 -> %pI4\n", 296 &iph->saddr, 297 &iph->daddr); 298 goto drop; 299 } 300 } 301 302 if (ip_options_rcv_srr(skb)) 303 goto drop; 304 } 305 306 return false; 307 drop: 308 return true; 309 } 310 311 int sysctl_ip_early_demux __read_mostly = 1; 312 EXPORT_SYMBOL(sysctl_ip_early_demux); 313 314 static int ip_rcv_finish(struct sk_buff *skb) 315 { 316 const struct iphdr *iph = ip_hdr(skb); 317 struct rtable *rt; 318 319 if (sysctl_ip_early_demux && !skb_dst(skb)) { 320 const struct net_protocol *ipprot; 321 int protocol = iph->protocol; 322 323 ipprot = rcu_dereference(inet_protos[protocol]); 324 if (ipprot && ipprot->early_demux) { 325 ipprot->early_demux(skb); 326 /* must reload iph, skb->head might have changed */ 327 iph = ip_hdr(skb); 328 } 329 } 330 331 /* 332 * Initialise the virtual path cache for the packet. It describes 333 * how the packet travels inside Linux networking. 334 */ 335 if (!skb_dst(skb)) { 336 int err = ip_route_input_noref(skb, iph->daddr, iph->saddr, 337 iph->tos, skb->dev); 338 if (unlikely(err)) { 339 if (err == -EXDEV) 340 NET_INC_STATS_BH(dev_net(skb->dev), 341 LINUX_MIB_IPRPFILTER); 342 goto drop; 343 } 344 } 345 346 #ifdef CONFIG_IP_ROUTE_CLASSID 347 if (unlikely(skb_dst(skb)->tclassid)) { 348 struct ip_rt_acct *st = this_cpu_ptr(ip_rt_acct); 349 u32 idx = skb_dst(skb)->tclassid; 350 st[idx&0xFF].o_packets++; 351 st[idx&0xFF].o_bytes += skb->len; 352 st[(idx>>16)&0xFF].i_packets++; 353 st[(idx>>16)&0xFF].i_bytes += skb->len; 354 } 355 #endif 356 357 if (iph->ihl > 5 && ip_rcv_options(skb)) 358 goto drop; 359 360 rt = skb_rtable(skb); 361 if (rt->rt_type == RTN_MULTICAST) { 362 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INMCAST, 363 skb->len); 364 } else if (rt->rt_type == RTN_BROADCAST) 365 IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST, 366 skb->len); 367 368 return dst_input(skb); 369 370 drop: 371 kfree_skb(skb); 372 return NET_RX_DROP; 373 } 374 375 /* 376 * Main IP Receive routine. 377 */ 378 int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev) 379 { 380 const struct iphdr *iph; 381 u32 len; 382 383 /* When the interface is in promisc. mode, drop all the crap 384 * that it receives, do not try to analyse it. 385 */ 386 if (skb->pkt_type == PACKET_OTHERHOST) 387 goto drop; 388 389 390 IP_UPD_PO_STATS_BH(dev_net(dev), IPSTATS_MIB_IN, skb->len); 391 392 if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL) { 393 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 394 goto out; 395 } 396 397 if (!pskb_may_pull(skb, sizeof(struct iphdr))) 398 goto inhdr_error; 399 400 iph = ip_hdr(skb); 401 402 /* 403 * RFC1122: 3.2.1.2 MUST silently discard any IP frame that fails the checksum. 404 * 405 * Is the datagram acceptable? 406 * 407 * 1. Length at least the size of an ip header 408 * 2. Version of 4 409 * 3. Checksums correctly. [Speed optimisation for later, skip loopback checksums] 410 * 4. Doesn't have a bogus length 411 */ 412 413 if (iph->ihl < 5 || iph->version != 4) 414 goto inhdr_error; 415 416 if (!pskb_may_pull(skb, iph->ihl*4)) 417 goto inhdr_error; 418 419 iph = ip_hdr(skb); 420 421 if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl))) 422 goto csum_error; 423 424 len = ntohs(iph->tot_len); 425 if (skb->len < len) { 426 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INTRUNCATEDPKTS); 427 goto drop; 428 } else if (len < (iph->ihl*4)) 429 goto inhdr_error; 430 431 /* Our transport medium may have padded the buffer out. Now we know it 432 * is IP we can trim to the true length of the frame. 433 * Note this now means skb->len holds ntohs(iph->tot_len). 434 */ 435 if (pskb_trim_rcsum(skb, len)) { 436 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INDISCARDS); 437 goto drop; 438 } 439 440 /* Remove any debris in the socket control block */ 441 memset(IPCB(skb), 0, sizeof(struct inet_skb_parm)); 442 443 /* Must drop socket now because of tproxy. */ 444 skb_orphan(skb); 445 446 return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL, 447 ip_rcv_finish); 448 449 csum_error: 450 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_CSUMERRORS); 451 inhdr_error: 452 IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS); 453 drop: 454 kfree_skb(skb); 455 out: 456 return NET_RX_DROP; 457 } 458